1. Field of the Invention
The present invention relates to an external storage device for an image pickup apparatus for backup storage of an image taken by the image pickup apparatus, and also to a control method therefor, an image pickup apparatus and an image management method.
2. Related Background Art
FIG. 18 is a schematic block diagram showing the configuration of a conventional digital camera, wherein a camera module 210 is composed of an image pickup lens 212, an image pickup element 214 of CCD type, an image pickup element control circuit 216 and an image processing circuit 218. When an image pickup operation mode is selected after the power supply is turned on, a CPU 220 initializes the camera module 210 and renders it operable, and also activates a display system composed of an LCD display device 222, a display drive circuit 224, an LCD control circuit 226 and a VRAM (video memory) 228. The LCD display device 222 functions as an electronic view finder and has a display ability of 640×480 pixels.
The image pickup element 214 converts an optical image, formed by the image pickup lens 212, into an electrical signal. The image pickup element control circuit 216 executes noise elimination and gain adjustment on the image signal outputted from the image pickup element 212 and converts the signal into a 10-bit digital signal for supply to the image processing circuit 218. The image processing circuit 218 applies processes such as white balancing, exposure adjustment, correction for flash exposure etc. to the image data from the image pickup element control circuit 216 and converts the image data into the YCbCr format (Y: luminance signal, Cb, Cr: color difference signals). In case the image pickup element 214 has about two million pixels, the image processing circuit 218 can process the image data of about 1600×1200 pixels, but processes the image data normally in a size of 320×240 pixels and 640×480 pixels at largest in the stage of displaying in the view finder.
The CPU 220 supplies the YCbCr image data from the image processing circuit 218 to the LCD control circuit 226 by DMA (direct memory access) method in a display size of 320×240 pixels. The LCD control circuit 226 once stores the YCbCr image data from the CPU 220 into the VRAM 228 after conversion into the RGB format, and then reads the image data from the VRAM 228 for supply to the display control circuit 224, which drives the LCD display device 222 according to the RGB data from the LCD control circuit 226. In this state, a monitor image (object image) of 320×240 pixels is displayed in an arbitrary portion in the image area of 640×480 pixels of the LCD display device 222.
By executing the process from the readout of the image pickup element 212 to the display on the LCD display device 222 in continuous manner with a cycle time of 1/30 seconds, an object image corresponding to the optical image entering the image pickup element 212 is constantly displayed on the image area of the LCD display device 222.
In case of taking an image, the user switches the apparatus to an image pickup mode. When a shutter switch 230 is depressed, the CPU 220 locks the set values of the white balancing, exposure adjustment, correction for flash photographing, etc., in the image processing circuit 218, and terminates the function of the LCD control circuit 226, the display drive circuit 224, and the LCD display device 222, in order to alleviate the load on the CPU 220.
In a view finder process, there is processed only a part of the image data of the image pickup element 212 in order to increase the processing speed, but the entire image data of 1600×1200 pixels are processed in the image pickup mode. More specifically, the image processing circuit 218 applies the aforementioned process to the image data of all the pixels of the image pickup element 214, and the CPU 220 writes the YCbCr image data from the image processing circuit 218 into an image development area 232a of a RAM 232. The CPU 220 also compresses the image data in the image development area 232a by a method based on the JPEG standard, and writes the compressed data in a folder prepared in advance in a flash memory 234 with a file name consisting of numerical data such as an arbitrary number of date data. Such folder is given a folder name based on a DCF (Design rule for Camera File system) standard of the digital still camera. The taken images are written in succession into such folder. In case of image taking by mounting the same memory card in a camera of another type, there is automatically prepared another file into which the taken image are stored.
The operation program and fixed data for the CPU 220 are stored in a ROM 236. There are also provided a chargeable battery 238 constituting a power source, and a DC/DC converter 240 for converting the output voltage of the battery 238 for supply to the CPU 220 and other circuit blocks. The CPU 220 is connected to a USB connector 244 through a USB module 242.
In the following there will be explained a reproduction mode for reproducing and displaying the taken image. When the image reproduction mode is selected by an unrepresented operation mode designation switch, the CPU 220 activates the LCD display device 222 thereby putting it in a standby state. The CPU 220 displays the folders, belonging to the apparatus and contained in the flash memory 234, in the image area of the LCD display device 222, and causes the operator to select one of the folders. When an image file to be displayed is designated after the folder selection, the CPU 220 reads and expands the designated file from the memory 234 and applies the YCrCb image data to the LCD control circuit 226. The LCD control circuit 226 once stores the YCrCb image data from the CPU 220 into the VRAM 228 after conversion into the RGB format, and then reads the image data from the VRAM 228 for supply to the display control circuit 224, which drives the LCD display device 222 according to the RGB data from the LCD control circuit 226. In this state, a reproduced image is displayed in the entire image area of 640×480 pixels of the LCD display device 222.
In case the image folder is not designated after the folder selection, the CPU 220 reads the image files of a designated number from the oldest date of image pickup, expands such image files and supplies the LCD control circuit 226 with the YCrCb image skipped to a smaller thumbnail size of 80×60 pixels. The LCD control circuit 226 converts the YCbCr image data of the plural images from the CPU 220 in succession into the RGB format, writes them into the VRAM 228 for simultaneous display, and then reads the image data of the plural thumbnail images from the VRAM 228 for supply to the display drive circuit 224 for the display in the wire image area. The display drive circuit 224 drives the LCD display device 222 according to the RGB data from the LCD control circuit 226, whereby plural thumbnail images are simultaneously displayed on the image area of 640×480 pixels of the LCD display device 222.
The CPU 220 also supplies the LCD control circuit 226 with image data including, for example, a warning about remaining battery capacity and various control messages, and the LCD control circuit 226 converts such image data into the RGB format and stores them in an address of the VRAM 228 corresponding to a display position, whereby the warning for the remaining battery capacity, etc., is displayed in a predetermined position in the image area of the LCD display device 222.
The CPU 220 can transfer the data, stored in the flash memory 234, to a device connected to the USB connector 244, such as a computer. For example a USB cable is connected to the USB connector 244, then a PC connection mode is set by the unrepresented operation mode designating switch and the other end of the USB cable is connected to the USB connector of the computer. Upon connection of the USB cable, the computer automatically identifies the device connected through the USB cable and activates a data fetching software. When the operator selects, with a mouse, one of the functions displayed on the display of the computer, the computer issues a command to the CPU 220 through the USB connector 244 and the USB module 242, and, based on such command, the CPU 220 reads the designated data from the flash memory 234 and transfers them to the computer.
The conventional digital camera utilizes, as the memory means for the taken images, not only the flash memory incorporated in the main body but also a detachable CF card utilizing a flash memory or a hard disk. The memory capacity of such external memory medium is more or less limited though it is recently increasing, it is necessary to transfer the stored data to another information memory device thereby securing the empty area. However, it is cumbersome to connect and activate the computer merely for the data backup, since the computer generally requires a long time for activation.
Even in case of backup of the taken image data in the computer, the data transferred to the computer are merely a copy of the image data. In case of reproducing the taken image again in the digital camera, there is required an operation of returning the taken image data (for example data of 1600×1200 pixels (about 700 kB)) from the computer to the flash memory 234, or an operation of reducing the data of 1600×1200 pixels to data of 640×480 pixels (about 35 kB) by an image conversion tool in the computer prior to transfer to the digital camera. The former operation reduces the empty area of the flash memory 234, while the latter operation involves a cumbersome operation.
There is recently proposed a receiving member (called a cradle) having functions not only of charging the rechargeable battery 238, but also of transferring the data stored in the flash memory 234 to the computer in response to the placement of the main body of the camera in a predetermined position or the start of charging of the rechargeable battery 238. However such receiving member is merely a charging device unless the computer is activated, and does not dispense with the procedure of activating the computer.